Device And Method For Roughing And Fine-Machining Of Gears

ABSTRACT

A method for cutting teeth into working gears using a tool, the tool main part of which has a plurality of cutting teeth which are arranged about a rotational axis and which protrude radially from the tool main part, the cutting teeth forming an end face, two tooth flanks which point away from each other, and cutting edges. The cutting edges are formed from the tooth flank edges adjoining the end face. In a first method step, tooth gaps which form tooth flanks are produced in the working gear by means of the cutting edges using a machining process in a first position of the tool relative to the working gear, and in a second method step, the working gear tooth flanks produced by the cutting edges are fine-machined by an abrasive tool surface.

TECHNICAL FIELD

The invention relates to a method for cutting teeth into working gearswith a tool, the main part of which has a multiplicity of teeth, whichare arranged about an axis of rotation, and which protrude radially fromthe main part of the tool, which cutting teeth have an end face, twotooth flanks facing away from each other, and cutting edges, wherein thecutting edges have cutting edges on the tooth flank edges adjoining theend face, wherein in a first method step, tooth gaps that form toothflanks are produced in the working gear by means of the cutting edgesusing a machining process in a first position of the tool relative tothe working gear, and in a second method step, the working gear toothflanks produced by the cutting edges are fine-machined by an abrasivetool surface. The invention further relates to a tool for execution ofthe method with a tool, the main part of which has a multiplicity ofteeth that are arranged about an axis of rotation, and which protruderadially from the main part of the tool, the said cutting teeth formingan end face, two tooth flanks facing away from each other, and cuttingedges on the edges of the tooth flanks adjoining the end face, for thegeneration by machining of tooth gaps forming tooth flanks on theworking gear. The invention further relates to a device for execution ofthe method with a tool, in which the electronic control device isprogrammed accordingly.

BACKGROUND

DE 10 2005 049 528 A1 and DE 10 2009 003 338 A1 describe methods for themachining of workpieces with internal or external tooth forms, whereinthe method is a hob skiving method. In the method there described, arough tooth form is first produced with a cutting tool. This takes placein a roughing operation. Following this first method step, the toothflanks are deburred in the region of their end face edges. In addition,the prior art includes WO2001/060733 A1, DE10305752 A1 and DE 3930322C1.

It is of known art to fine-machine the tooth flanks of such rough toothforms by honing or grinding. In the case of honing, a honing wheelclamped on a honing spindle is used for this purpose, whose honing teethengage with the tooth forms produced in the working gear. The honingteeth engage in the manner of a meshing gear with the teeth of theworking gear. The tool axis of rotation and the working gear axis ofrotation have an axis crossing angle relative to each other, so thatwhen sliding the tooth flanks of the working gear and the tool past eachother a surface transverse movement takes place, which results in aremoval of material from the working gear flank.

SUMMARY

The invention has for its object the further advantageous development ofthe processing method of known art in its use, and for this purpose tospecify a suitable tool and a suitable device.

The object is achieved by the invention specified in the claims, whereinthe dependent claims are not only advantageous developments of theinvention specified in the coordinate claims, but also representindependent solutions of the task.

First and foremost, it is proposed that the tool has abrasive toothflanks. With the tool, two production steps of a manufacturing processconsisting of a plurality of successive production steps can beexecuted. This preferably takes place without an intermediate toolchange, but simply by an alteration of the position of the tool axis ofrotation relative to the workpiece axis of rotation. In a first methodstep, the cutting edges of the tool are used to produce the tooth formsof the working gear. The production of the tooth forms of the workinggear can be carried out in a plurality of successive machiningoperations, for example in a plurality of successive hob skiving processsteps in which initially a rough tooth form, and subsequently a finetooth form, are generated. However, it is also possible to produce thetooth form in a single hob skiving process step, wherein in particularprovision is made for the tooth formation to be executed in a pluralityof successive steps with one tool, wherein between the individual stepsit is just the distance between the working gear axis of rotation andthe workpiece axis of rotation that is changed, so that the tooth gapsgenerated by the cutting edges are deepened step-by-step. In the case ofhob skiving the cutting edges of each cutting tooth engage in a skivingmanner with the material of the working gear, wherein a feed of thecontinuously rotationally driven workpiece spindle relative to the toolspindle of the teeth to be produced is provided in the direction ofextent of the teeth. Processing takes place at a first axis crossingangle between the tool axis of rotation and the working gear axis ofrotation. The cutting edges are formed by the edge at which the toothflanks of the cutting tooth transition into an end face of the cuttingtooth. The cutting wheel can take the form of a cutting wheel with astep cut or a conical surface cut. However, the cutting wheel can alsohave a plane end face, in which the end faces of the cutting teeth arealso located. In a second process step in accordance with the invention,the tooth flanks of the working gear produced by the cutting edges ofthe tool are fine-machined. This takes place in accordance with theinvention by means of an abrasive tool surface in the manner of a honingprocess. For this purpose, provision is made for the abrasive toolsurfaces to be formed on the tooth flanks of the tool. By an adjustmentof the relative position of the tool and working gear these are broughtinto a second position, which differs from the first position, in whichthe tooth flanks of the working gear can be surface processed. Thistakes place essentially by altering the axis crossing angles between theworking gear axis of rotation and the tool axis of rotation, and byaltering the axial distance, that is to say, by a spatial displacementof the workpiece and/or tool relative to each other. While in the firstposition, when generating the tooth forms, clearance angles existbetween the tooth flanks of the working gear and the tooth flanks of thecutting wheel; in the second position, when fine-machining, the toothflanks of the tool roll from the tooth flanks of the working gear, sothat surface processing of the tooth flanks of the working gear takesplace by means of abrasive tool surfaces. The position of the toolrelative to the working gear is essentially changed by the alteration ofthe axis crossing angle, such that the clearance angles required in thefirst method step disappear, so that the cutting teeth engage in themanner of a meshing gear with the tooth gaps of the working gear. Thecutting teeth have a direction of extent relative to the axis of thetool, such that in the second process step, a surface transversemovement takes place between the mutually engaging tooth flanks.

The tool in accordance with the invention for the execution of theabove-described method has a main part that has a multiplicity ofcutting teeth, arranged about an axis of rotation and protrudingradially from the main part of the tool. The said cutting teeth havecutting edges at least on their end faces, wherein the cutting edges runalong the edges on which the end faces transition into the tooth flanksof the cutting teeth. In their direction of extent the cutting teethpossess an essentially constant cross-section. The vertex lines laid onthe tips of the cutting teeth preferably run on a cylindrical surface.However, it is also envisaged that the vertex lines could run on atruncated conical surface. While the cutting edges are used formachining the tooth gaps of the working gear forming the tooth flanks,the tooth flanks of the tool adjacent to the cutting edges can be usedfor the fine-machining of the tooth flanks of the working gear generatedby the cutting edges. For this purpose, the tooth flanks of the tool areabrasively formed. The tooth flanks of the tool are abrasively formedsuch that a movement of the tooth flanks of the tool relative to thetooth flanks of the working gear leads to a honing or grinding removalof material from the flank of the tooth of the working gear. Theabrasive tooth flank of the tool is preferably formed by a coating. Hereit can take the form of a hard material coating. For this purpose, ametallisation can be applied onto the tooth flanks, in which the hardmaterial particles are embedded in a manner of known art. For example,the tooth flanks of the tool are nickel plated. A nickel binding layeris applied onto a nickel base layer, in which binding layer a pluralityof hard material particles are embedded; a portion of their surfacesprotrude from the metal layer, so as to remove material, in the mannerof a dressing tool for honing stones, from the tooth flanks of theworking gear. The hard material particles can take the form of boronnitride, aluminium oxide, or diamond particles.

The invention also relates to a device for the execution of the method;in a manner of known art the device possesses at least one workpiecespindle and one tool spindle. The workpiece spindle and the tool spindlecan each preferably be rotationally driven by rotary drive units. Herethe latter can take the form of servomotors, in particular torquemotors, or synchronous motors. In principle, however, it is sufficientfor the execution of the method if just one spindle can be rotationallydriven by an electric drive. Preferably, however, both spindles, that isto say, the tool spindle and the workpiece spindle, can be rotationallydriven by a rotary drive. The two rotary drives are synchronised so thatthey rotate synchronously. Means are also provided, for example in theform of a cross table, with which the tool can be advanced relative tothe working gear, wherein the feed essentially takes place in thedirection of extent of the tooth flanks of the working gear. Forpurposes of generating the feed either the tool or the working gear canbe moved relative to a machine frame. Furthermore means are provided bywhich the axis crossing angle between the tool axis of rotation and theworkpiece axis of rotation can be adjusted. All means for adjustment cantake the form of stepper motors and/or torque motors. The device has anelectronic, programmable controller with which the individual axes ofthe machine tool can be controlled. The control device is programmedsuch that the machine tool operates with the above-described tool inaccordance with the above-described method.

BRIEF DESCRIPTION OF THE DRAWINGS

In what follows the invention will be described in more detail with theaid of an example of embodiment. Here:

FIG. 1 shows schematically a tool 2 in the form of a gear, whose cuttingteeth 3 are in meshing engagement with the teeth of a working gear 1; itillustrates the position of the working gear 1 relative to the tool 2 ina first method step in which a tooth form is generated in the workinggear 1;

FIG. 2 shows the arrangement as in FIG. 1, but in the viewing directionII as in FIG. 1;

FIG. 3 shows the arrangement in FIG. 1, but in a plan view onto theworking gear 1;

FIG. 4 shows at an enlarged scale the engagement of the cutting teeth 3shown in FIG. 3 with the tooth gaps 17 between the teeth 13 of theworking gear 1; it illustrates the clearance angle between the toothflanks of the cutting teeth 3 and the teeth 13;

FIG. 5 shows a perspective view of the tool, whose cutting edges 18, 19are formed by the edges at which the abrasively coated tooth flanks 6,6′ of the cutting teeth 3 meet the end faces 7 of the cutting teeth 3;

FIG. 6 shows a representation as in FIG. 1, but in a second position inwhich the axis crossing angle between the working gear axis of rotation4 and the tool axis of rotation 5 has been altered, and in addition theposition of the tool 2 has been displaced in the direction of the toolaxis of rotation 5, so that the abrasive tooth flanks 6, 6′ can processthe tooth flanks 14, 14′ of the tooth forms of the working gear 1.

FIG. 7 shows a representation as in FIG. 2, but in the second position;

FIG. 8 shows a representation as in FIG. 3, but in the second position;

FIG. 9 shows the detail IX in FIG. 8 so as to clarify the engagement ofthe cutting tooth 3 with the tooth gaps 17 between the teeth 13 of theworking gear 1, wherein no clearance angle is present between the toothflanks 6, 6′ of the cutting teeth 3 and the tooth flanks 14, 14′ of theteeth 3 of the working gear 1, but an abrasively formed tooth flank 6′of the cutting tooth 3 engages in surface contact with the tooth flank14′ of a tooth 13 of the working gear 1;

FIG. 10 shows a representation as in FIG. 9, but after the working gear1 and the tool 2 have been slightly further rotated, so that theabrasively formed tooth flank 6 of the cutting tooth 3 is in surfacecontact with the tooth flank 14 of a neighbouring tooth of the workinggear 1;

FIG. 11 shows at an enlarged scale the detail XI in FIG. 1;

FIG. 12 shows the section XII-XII in FIG. 11, and

FIG. 13 shows schematically a device for the execution of the method.

DETAILED DESCRIPTION

FIG. 13 shows very schematically a device for the execution of themethod. Devices 24, 25 are fixed on a machine frame, not shown, withwhich devices a workpiece spindle drive 9 and a tool spindle drive 10can be adjusted relative to each other. The adjustment isprogram-controlled by an electronic control device 23. The means ofsetting and adjustment 24, 25 are able to relocate the relativepositions of the workpiece spindle drive 9 and the tool spindle drive 10relative to each other. A working gear spindle 21 is rotationally drivenby the workpiece spindle drive 9; the spindle carries a working gear 1.The working gear 1 is rotationally driven about a working gear axis ofrotation 4.

The tool spindle drive 10 drives a tool spindle 22, which carries agear-form tool 2, which can be rotationally driven about a tool axis ofrotation 5.

By means of the means of setting and adjustment 24, 25 the axis crossingangles a, 13 of the working gear axis of rotation 4 can be set relativeto the tool axis of rotation 5. In addition, a feed can be implemented.

The tool shown in FIG. 5 has a tool main part 11, which can be clampedon a tool spindle 22 in order to drive the tool main part 11 about thetool axis of rotation 5.

From the tool main part 11 a plurality of cutting teeth 3 protrude inthe radial direction relative to the tool axis of rotation 5. Thecutting teeth 3 possess a constant cross section over their entire axialextent. In the embodiment, the vertex line 3′ drawn through the toothheads 8 of the cutting teeth runs at an angle to the tool axis ofrotation 5. The vertex lines 3′ can lie on a cylindrical surface aboutthe tool axis of rotation 5 or on a truncated conical surface about thetool axis of rotation 5. Depending on the processing task, the cuttingteeth 3 preferably extend in a uniform angular distribution about thetool axis of rotation 5.

Each of the cutting teeth 3 possesses an end face 7, which with theformation of an edge intersects two tooth flanks 6, 6′ of the cuttingtooth 3 facing away from each other in the circumferential direction.The edge forms cutting edges 18, 19. In the embodiment, one cutting edge19 is formed by a groove and the opposing cutting edge is formed by achamfer, so that both cutting edges of the oblique cutting teeth 3 cancut into the workpiece with the same rake angle, although the end face 7is a surface radial to the tool axis of rotation 5.

In an alternative embodiment, the edges between the end face 7 and thetooth flanks 6, 6′ run at right angles or at acute angles. The end faceof the cutting tool 2 then possesses a step cut.

The tooth flanks 6, 6′ are abrasively formed. For this purpose,provision is made in particular for the tooth flanks 6, 6′ to carry ametal layer 28, in particular a nickel layer, in which hard materialparticles 27, in particular diamond particles, are embedded, whichprotrude with surface sections out of the metal layer 28 in order togenerate an abrasive action. The metal layer 28 can be a binding layerthat has been deposited on a substrate layer 26 applied directly ontothe steel main body of the tooth flank 14. The substrate layer 26 andthe binding layer 28 can be galvanically applied metal layers, inparticular nickel layers.

With the tool 2 in accordance with the invention, it is possible, in afirst process step, which is shown in FIGS. 1 to 4, to incorporate atoothed form into a working gear 1 with no tooth form, or with a roughtooth form, or with a rough initial tooth form. This takes place in afirst roughing step, which can also be followed by a fine-machiningstep, in which the cutting edges 18, 19 enter into the working gear 1with a lower feed and a lower cutting power.

In accordance with the invention, the first process step illustrated inFIGS. 1 to 4, in which the tooth form is produced, is followed by thesecond process step shown in FIGS. 6 to 10, in which the tooth flanks14, 14′ of the working gear 1 are fine-machined with the same tool 2,not with its cutting edges 18, 19, but instead with the abrasivelyequipped tooth flanks 6, 6′.

In the first method step, illustrated in FIGS. 1 to 4, the tool spindle22 is presented to the workpiece spindle 21 at an axis crossing angleα₁, β₁ such that with a synchronised rotation of the workpiece spindle21 and the tool spindle 22 and a feed in the direction of extent of theteeth 13 of the working gear 1 a skiving process takes place, duringwhich the tooth flanks 14, 14′ of the tooth gaps 17 are generatedbetween the teeth 13 of the working gear 1. Here the tooth flanks 6, 6′of the tool have a wedge-shaped separation distance from the toothflanks 14, 14′ of the teeth 13 of the working gear 1. This clearanceangle can be seen in FIG. 6.

In the first process step, the tooth gaps 17 can be deepened in astep-by-step manner.

In a second process step, which preferably follows immediately after thefirst process step, and which is shown in FIGS. 6 to 10, tooth flankprocessing of the tooth flanks 14, 14′ takes place. For this purpose,the axis crossing angle, and/or the spatial location of the toolrelative to the workpiece, is altered. In the second position, for theexecution of the second method step, the axis crossing angles α₂, β₂ areset such that the clearance angle between the tooth flanks 6, 14, and6′, 14′ respectively, disappears. FIG. 9 shows that an abrasively coatedtooth flank 6′ of the cutting tooth 3 is in surface contact with thetooth flank 14′ of a tooth 13 of the working gear 1. In the secondprocess step, if the gear-form cutting tool 2 and the toothed workinggear 1 are rotated relative to one another with intermeshing teeth, thetooth flanks 6′ roll from the tooth flanks 14′. On account of the axiscrossing angles α₂, β₂ a grinding movement takes place. A surfacetransverse movement occurs, such that the abrasive particles of thetooth flank 6′ remove material from the tooth flank 14′.

FIG. 10 shows an operating position that directly follows the operatingposition shown in FIG. 9 if the two intermeshing gear-form bodies of theworking gear 1 and the tool 2 have been slightly further rotated. In themanner of a meshing gear, the tooth flank 6, located opposite the toothflank 6′ and similarly abrasively coated, engages with the tooth flank14 of the working gear 1, located opposite the tooth flank 14′, so as tofine-machine the latter by the abrasive removal of material.

The above statements serve to explain the inventions recorded as a wholeby the application, which develop the state of the art at least by thefollowing combinations of features, and also independently, namely:

A method, which is characterised in that the abrasive tool surfaces areformed by the tooth flanks 6, 6′ of the tool 2, which in the secondmethod step operates on the working gear 1 in a second position, whichdiffers from the first position.

A method, which is characterised in that in the first position the toothflanks 6, 6′ of the tool 2 have a clearance angle relative to the toothflanks 14, 14′ of the working gear 1.

A method, which is characterised in that in the second position forsurface processing the tooth flanks 6, 6′ of the tool 2 roll from thetooth flanks 14, 14′ of the working gear 1.

A method, which is characterised in that the tool axis of rotation 5 andthe working gear axis of rotation 4 assume different axis crossingangles α₁, β₁, α₂, β₂ in the two positions.

A method, which is characterised in that the first process step is a hobskiving process.

A method, which is characterised in that the second process step is aprocess step similar to honing, wherein the cutting teeth 3 engage inthe manner of a meshing gear with the tooth gaps 17 of the working gear1.

A method, which is characterised by a surface transverse movement asdetermined by the axis crossing angles α₂, β₂ of the tooth flanks 6′,14′, 6, 14, which engage with each other in the second process step.

A tool, which is characterised in that the tooth flanks 6, 6′ of thetool 2 are abrasively formed for the fine-machining of the tooth flanks14, 14′ of the working gear 1 generated by the cutting edges 18, 19.

A tool, which is characterised in that the tooth flanks 6, 6′ of thetool 2 are abrasively coated, and in particular have a hard materialcoating 26 to 28.

A tool, which is characterised in that the tooth flanks 6, 6′ of thetool 2 have hard material particles 27, in particular boron nitride,aluminium oxide, or diamonds, embedded in a metal layer 28, inparticular a nickel layer.

A tool, which is characterised in that the direction of extent of thecutting teeth 3 runs at an angle to the axis of rotation 5.

A tool, which is characterised in that a vertex line 3′ of the cuttingteeth 3 runs on a truncated conical surface, or a cylindrical surface,about the axis of rotation 5.

A device, which is characterised in that the control device 23 isequipped such that in a first step in a first position of the tool 2relative to the working gear 1 tooth flanks 14, 14′ forming tooth gaps17 in the working gear 1 are produced with the cutting edges 18, 19 bymeans of a machining process, and in a second method step, the toothflanks 14, 14′ of the working gear 1 generated by the cutting edges 18,19 are fine-machined by an abrasive tool surface, which is formed by thetooth flanks 6, 6′ of the tool 2, wherein the second process step isperformed in a second position that differs from the first position.

All disclosed features are essential to the invention (bothindividually, and also in combination with one another). In thedisclosure of the application, the disclosure content of theassociated/attached priority documents (transcript of the priorapplication) is hereby also incorporated in full, also for the purposeof incorporating features of these documents in the claims of thepresent application. The subsidiary claims characterise with theirfeatures independent inventive developments of the prior art inparticular in order to make divisional applications on the basis ofthese claims.

1-7. (canceled)
 8. A tool for cutting the teeth of working gears with amain part, which has a multiplicity of cutting teeth arranged about anaxis of rotation and protruding radially from the main part of the tool,which cutting teeth have an end face, two tooth flanks facing away fromeach other, and cutting edges on the edges of the tooth flanks adjacentto the end face for the generation by machining of tooth gaps formingtooth flanks on the working gear, the tooth flanks of the tool areabrasively formed for the fine-machining of the tooth flanks of theworking gear generated by the cutting edges
 9. The tool in accordancewith claim 8, wherein, the tooth flanks of the tool are abrasivelycoated, in particular have a hard material coating.
 10. The tool inaccordance with claim 8, wherein, the tooth flanks of the tool have hardmaterial particles, in particular boron nitride, aluminium oxide, ordiamonds, embedded in a metal layer, in particular a nickel layer. 11.The tool in accordance with claim 8, wherein, the direction of extent ofthe cutting teeth runs at an angle to the axis of rotation.
 12. The toolin accordance with claim 8, wherein, a vertex line of the cutting teethruns on a truncated conical surface, or a cylindrical surface, about theaxis of rotation. 13-14. (canceled)